1. Field of the Invention
The present invention relates to rotary separators, and in particular to a rotary separator having a discharge operable in response to pressure exerted by separated material in the separator vessel.
2. Background of the Invention
Rotary separators for separating a solid-liquid mixture are known in the art which consist of opposed conical upper and lower sections having an annular gap therebetween. Such separators are symmetrical about the axis of rotation such that when the separation vessel is rotated the solid component accumulates at the area of greatest radius of the vessel and is drawn off through the annular gap.
A separator as described above is known, for example, from U.S. Pat. No. 3,823,868. As disclosed in that patent, the opening and closing of the annular gap is achieved by the use of a piston valve which surrounds the lower part of the separator vessel. The piston valve is axially movable and is fixed in a closed position by means of a spring and, together with the exterior wall of the lower part of the separator vessel, forms an annular pressure chamber into which a fluid is introduced in order to open the piston valve and allow discharge through the annular gap.
The piston valve disclosed in U.S. Pat. No. 3,823,868 slides in a metallic guide the purpose of which is to allow axial displacement of the valve without tilting, so that discharge is uniform around the entire circumference of the separator. In order to achieve such uniform discharge without tilting of the valve it is essential that the entire effective surface of the piston valve be uniformly charged with hydraulic fluid. This means that in terms of tolerances the piston valve, the metallic guide and the appertaining seals utilized in the construction of such separators must be designed not only to account for the deformations to be expected in the centrifugal force field, but also must account for differing temperatures of the solid-liquid mixture to be separated. In order to afford the widest possible range of use for such a separator, optimum values must be chosen so that when mechanical and/or thermally conditioned expansions result which deviate from the optimum values, effective and efficient separation and discharge is diminished.
It is therefore a problem in the art to achieve uniform discharge from a rotary separator in a manner which can be varied according to thermal and mechanical conditions associated with each type of mixture to be separated.